If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1854
Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88
my SSTC is finished and i hooked it up to half wave rectified mains, the sparks were only 3 cm. i found this weird so i decided to scope the halfbridge.
and i saw a lot of ringing. is this normal. if not how can i supress it, and does the ringing on the output affect the spark length.
i have a scope image but i can't insert it in a edit ?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
A bit of googling would reveal alot.
But, since the thread is already started...
There will always be some ringing, but depending on what 'bad' is, it needs to be fixed. Suppressing ringing means reducing parasitic inductance. This means short wires, that are closer together, to give small loop distance. A GDT with gaps between the wire and the core is extra inductance, also known as leakage inductance. That would be symbolized by an inductor in series with the GDT, because it is, essentially, the same thing electronically. The turns should be as close to the cor as possible.
Wires from the GDT/to the GDT should be very short when possible. Since you are running a halfbridge, the primary of the GDT is 2 times more important than either one of the secondarys. It is still mandatory that you shorten secondary leads, where possible. This is how i did mine:
Any traces on the driver should be small, and close to each other, when possible. A ground plane is even better.
Ringing that reduces spark length would be very severe. It usually just results in switching losses that kill MOSFETs from heat. Shoot-through does the same, but that is something totally different...
Registered Member #347
Joined: Sat Mar 25 2006, 08:26AM
Location: Vancouver, Canada
Posts: 106
Could you post a schematic/photo of your bridge, and a zoomed in scope shot of the ringing?
Ringing like that may be caused by slow turn-off (reverse recovery) of the MOSFET body diodes, are you bypassing the body diodes with ultrafast rectifiers? The scope shot below shows ringing due to reverse recovery in a DRSSTC (Ch1 and Ch3 are the two bridge outputs), but it's nowhere near as bad as your ringing. If you could take a similar zoomed in shot it would be helpful in determining what's going on.
Registered Member #1854
Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88
yes i have ultra fast rectifiers who are disableing the mosfet body diode, one fast recovery diode in series with the FET and 1 ultra fast diode over the whole thing. so the body diode is fully disabled
what i tried now is shorten the wires as much as possible, and it worked alot less ringing but still al little bit, i also put a ELCO on the bridge supply together with a 2.2nF ceramic cap. that also suppressed the ringing a bit.
but i try to get a scope shot as soon as i can, for more details but getting a zoomed shot, i will need a good triggering on my PC scope and because of the ringing i sometimes can't get a good trigger but i will try.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
lots of ringing
